Venlafaxine, (±)-1-[2-(Dimethylamino)-1-(4-ethyoxyphenyl)ethyl]cyclo-hexanol, having the following formula I, is the first of a class of anti-depressants. Venlafaxine acts by inhibiting re-uptake of norepinephrine and serotonin, and is an alternative to the tricyclic anti-depressants and selective re-uptake inhibitors. 
U.S. Pat. No. 4,535,186 (the '186 patent) describes the process for the preparation of venlafaxine hydrochloride via the intermediate venlafaxine base. The entirety of the '186 patent is incorporated herein by reference. However, the '186 patent does not describe whether the venlafaxine so obtained is solid.
The existence of certain polymorphs of venlafaxine hydrochloride is mentioned in the European patent application EP 0 797 991 A1.
In the Summary Basis of Approval of New Drug Application No. 20-151 (venlafaxine hydrochloride tablets) and No. 20-699 (venlafaxine extended release capsules), three polymorphic forms of venlafaxine hydrochloride are mentioned.
We have now found a novel process for isolating venlafaxine as a solid. The isolated venlafaxine is in the form of white crystals, with a purity of 99.3% or greater as confirmed by high pressure liquid chromatography (HPLC).
We have found that crystalline venlafaxine can be prepared from venlafaxine hydrochloride by methylation of N,N-didesmethyl venlafaxine by means of a novel process.
We have found two novel polymorphs of venlafaxine hydrochloride (denominated Form I and Form II) and two novel solvate forms (denominated Form III and IV).
We have found a process for preparing venlafaxine hydrochloride from venlafaxine base and hydrochloric acid (HCl) gas in acetone or isopropanol. We have found the application of such process for preparing venlafaxine hydrochloride Form I and Form II.